Conventional positive displacement pumps pump liquids in and out of a pumping chamber by changing the volume of the chamber. Many pumps are bulky with many moving parts, and are driven by a periodic mechanical source of power, such as a motor or engine. Often such pumps require mechanical linkages, including gearboxes, for interconnection to a suitable source of power.
Other types pumps, as for example disclosed in U.S. Pat. No. 5,64 1,270; and German Patent Publication No, DE 4032555A1 use an actuator made of a magnetostrictive material. As will be appreciated, magnetostrictive material change dimensions in the presence of a magnetic field. Numerous magnetostrictive materials are known. For example, European Patent Application No. 923009280 discloses many such materials. A commercially available magnetostrictive material is sold in association with the trademark TERFENOL-D by Etrema Corporation, of Ames, Iowa.
These magnetostrictive pumps rely on the expansion and contraction of a magnetostrictive element to compress a pumping chamber. Known magnetostrictive pumps however compress a single pumping chamber. As such, these pumps produce a single pumping compression stroke for each cycle of contraction and expansion of the magnetostrictive material. This, in turn, may result in significant pressure fluctuations in the pumped fluid. The flow rate is similarly limited to the displacement of the single-pumping chamber. Moreover, pumps with a single actuator may be mechanically imbalanced and thereby prone to mechanical noise and vibration as the single actuator expands and contracts.
In certain applications, constant pressures and high flow rates per unit weight of a pump are critical. For instance, in fuel delivery systems in aircrafts, pump designs strive to achieve low pump weight to fuel delivery ratios, while still providing for smooth fuel delivery.
Accordingly, an improved magnetostrictive pump facilitating high flow rates, and smooth fluid delivery would be desirable.